Magnetostrictive element



April 1, 1958 H. J. ROUND ETAL. 2,829,047

MAGNETOSTRICTIVE ELEMENT Filed April 2. 1954 Harney States 2,829,047 MAGNETOSTRICTIVE ELEMENT Application April 2, 1954, Serial No. 420,646

Claims priority, appiicajtion Great Britain April` 2, 1953 8 Claims. (Cl. 75-170) Magnetostrictive devices are used for the conversion of electrical to mechanical oscillations and vice versa, for example as transducers in echo-sounding apparatus. A measure of the efficiency of the magnetostrictive device is given by its electromagnetic coupling coetlicient (K). This coeicient may be determined experimentally and depends upon the material of the magnetostrictive element.

The material commonly used for magnetostrictive elements is commercially pure nickel, which combines a high electromagnetic coupling coefficient in magnetic fields of low and medium strengths with high resistance to corrosion. t

An object of this invention is to improve the eiciency of magnetostrictive devices.

The present invention is based on the discovery that the addition of small quantities of cobalt to the nickel improves theV coupling coefficient at low and medium field strengths.

According to the invention, a magnetostrictive element, for instance the vibrator of an echo-sounding device, is made of a binary alloy of nickel and cobalt containing from 2 to 6%, and preferably'4% cobalt. In making the alloys commercially pure nickel is normally used, and accordingly the usual impurities will also be present. Commercial nickel often contains very smallv quantities of cobalt, and on occasions the cobalt may be as high as The cobalt content of the alloys used according to the invention is higher than the highest amount of cobalt ever present as an impurity in commercial nickel.

The variation of the magnetic properties with the cobalt `content is shown in the accompanying graphical drawing,

in which the abscissae are the cobalt contents of nickel-. cobalt alloys tested and theordinates are the`values of the coeicientK.

The curve shows the way in which the coeicient K was found to vary in one ring transducer. The coefficient wasv measured at a frequency of 33,000 cycles per second and at remanence, i. e. in the absence of an externally applied biasing magnetic eld. It will be seen,

that pure nickel gave a value of K of 16%, and with 1% cobalt, which may be regardedas commercial nickel of rather highV cobalt content, K was 20%. At 2% cobalt, however, K had risen to 24% and vat 4% cobalt to 30%. As the cobalt content increased further the value of K began to fall again, being `23% at 6% cobalt. This graph is proof of the critical nature of the cobalt content, and

of the advantage obtained by making the cobalt content from 2 to 6%, i. e. distinctly above that of any commercial nickel.

Patented Apr. v1, 1958 A substantially similar curve is obtained on measuring the maximum coetlicient K in a biasing eld.

We claim:

1. A transducer vibrator element exhibiting magnetostrictive properties made of a binary alloy consisting of nickel and cobalt containing from 2 to 6% cobalt to provide high eiiiciency in the conversion of mechanical energy into electrical energy or vice versa.

2. A transducer vibrator element according to claim v1 in which the cobalt content is 4% to provide high eiciency in the conversion of mechanical energy into electrical energy or vice versa.

3.. A transducer for converting mechanical energy into electrical energy or vice versa having a magnetostrictive element consisting essentially of a binary alloy consisting of nickel and cobalt containing from about 2% Vto about 6% cobalt to provide high eiciency in the conversion of mechanical energy into electrical energy or vice versa.

4. A transducer for converting mechanical energy into electrical energy or vice versa having a magnetostrictive element consisting essentially of a binary alloy consisting of nickel and cobalt containing about 4% cobalt to provide high eficiency in the conversion ofVV mechanical energy into electrical energy or vice versa.

5. An echo-sounding device having a transducer for converting mechanical energy into electrical energy or Vice versa having a magnetostrictive element consisting essentially of a binary alloy consisting of nickel and cobalt containing from about 2% to about 6% cobalt to provide high efciency in the conversion of mechanical energy into electrical energy or vice versa.

6. An echo-sounding device having a transducer for converting mechanical energy into electrical energy or vice versa having a magnetostrictive element consisting essentiallyof a binary alloy consisting of nickel and cobalt containing about 4% cobalt to provide high eiiciency in the conversion of mechanical energy into electrical energy or Vice versa.

7. A transducer element exhibiting magnetostrictiveV properties constructed of a binary alloy consisting of nickel and cobalt containing about 2% to about 6% cobalt to provide high eiciency in the conversion of mechanical energy into electrical energy or vice versa,

8. A transducer element exhibiting magnetostrictive properties constructed of a binary alloy' consisting of nickel and cobalt containing about 4% cobalt to provide high efficiency Vin the conversion of mechanicalenergy into electrical energy or vice versa.

References Cited in the le of this patent UNITED STATES PATENTS v Acker Mar. 2,

OTHER REFERENCES Ferromagnetism, by Bozorth, published .by Van Nostrand, 1951, pages 672-674. 

1. A TRANSDUCER VIBRATOR ELEMENT EXHIBITING MAGNETOSTRICTIVE PROPERITIES MADE OF A BINARY ALLOY CONSISTING OF NICKEL AND COBALT CONTAINING FROM 2 TO 6% COBALT TO PROVIDE HIGH EFFICIENCY IN THE CONVERSION OF MECHANICAL ENERGY INTO ELECTRICAL ENERGY OR VICE VERSA. 